Neutron diffraction study on the Xe behavior in clathrate hydrate analyzed by Rietveld/maximum entropy method

We analyzed the neutron scattering length density distributions of xenon deuterohydrate by Rietveld and maximum entropy method analyses to clarify the Xe motion behaviour in the clathrate cages. The crystal structure of Xe hydrate was refined as a structure I type clathrate hydrate which consists of 46 ice molecules in a framework of two dodecahedral cages (small cages) and six tetrakaidecahedral cages (large cages). In the small cage, a spherical nuclear density attributed to the Xe atom was observed at the center of the cage. On the other hand, an ellipsoid shaped nuclear density distribution was observed at the center of the large cage; the major axis of the ellipsoid nuclear density was directed toward the center of a hexagonal facet of the large cage. The distributions phenomena of the Xe atom in the both cages were independent of temperature.